Experts differ on environmental effect of ‘brown clouds’

Words of warning: The Dokriani glacier in the Garhwal Himalayas. A UN report last week concluded that the atmospheric brown cloud over Asia is dimming 13 mega cities and causing glaciers to melt. D.P.

Updated: Sun, Nov 23 2008. 11 49 PM IST

Bangalore: Even as Union science and technology minister Kapil Sibal dismissed a United Nations Environment Programme (UNEP) report last week which said the atmospheric brown cloud over Asia is dimming 13 mega cities and causing Himalayan glaciers to melt, scientists behind the report are pointing to clear scientific evidence behind the report’s conclusions.

According to the report, the first part of which was released in 2002 amid much global alarm and criticism, brown clouds arising from burning of fossil fuels and biomass are dimming New Delhi, Kolkata and Mumbai, besides 10 other cities in the region.

Words of warning: The Dokriani glacier in the Garhwal Himalayas. A UN report last week concluded that the atmospheric brown cloud over Asia is dimming 13 mega cities and causing glaciers to melt. D.P. Dobhal, Wadia Insitute of Himalayan Geology, Dehradun

New Delhi is getting darker by 10-25%, and the rest of India has been facing this trend at the rate of 2% per decade between 1960 and 2000, but one that is doubling between 1980 and 2004.

Scientists, led by V. Ramanathan of Scripps Institution of Oceanography in La Jolla, California, say the cloud, which is leading to an extreme weather system, harming health and agriculture in the region, could also provide an answer to why the warming trend in “India’s night time temperatures is much larger than the trend in daytime temperatures”.

“We all know pollution is increasing and is bad for health, agriculture and so on, even though there is no political will to fight it… But I’d question whether there is evidence showing soot on the glacier,” retorts J. Srinivasan, professor at the Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science in Bangalore.

Snow reflects solar radiation, but if there is soot or carbon deposit on it, then snow absorbs light and begins to melt.

Srinivasan had questioned the 2002 report’s finding that the cloud was “modifying the mighty monsoon”, arguing that brown haze, and not cloud, as the UN report termed it, was found elsewhere as well and that its direct impact on the monsoon was suspect.

Indeed, the scientists behind the cloud findings say this time that the brown clouds are elsewhere too, including over parts of North America, Europe, southern Africa and the Amazon basin, requiring “urgent and detailed research”.

As to evidence of carbon on Himalayan glaciers, Ramanathan says the criticism “is not true”.

“The Chinese have dug ice cores in Tibetan Himalayas and clearly have documented black carbon in ice,” he told Mint.

His own programme, called Quantifying Himalayan glacier melt by atmospheric brown clouds, has set up a black carbon site in the foothills of Mt Everest and has found a “lot of black carbon in the air close to the surface”.

India has never done any systematic study of any Himalayan glacier, notes Syed Iqbal Hasnain, glaciologist at The Energy and Resources Institute in New Delhi.

In collaboration with Norway and Iceland, Hasnain set up a weather station earlier this month in Kashmir to study the Kolahoi glacier.

“We’d like to include this glacier in a list of benchmark glaciers which are necessary for long-term studies,” he says, noting that his team will drill the ice to study the “mass change” in the glacier.

He is organizing a meeting of experts in Kathmandu in early December, following which the international ABC group may join his study.

“From field studies we do see haze in this glacier but some definitive trends will emerge only in two-three years,” Hasnain adds.

However, there still remains a significant question: How does one determine if the melting is due to soot or due to the greenhouse effect?

“This is difficult (to answer),” says Ramanathan. The way it is done is through models in which one estimates the warming due to greenhouse effect and then due to soot.

“These sort of models indicate both are contributing to melting,” he adds.